Semiconductor device and method of manufacturing the same

Abstract

A semiconductor device includes a substrate having an active region, and first to third transistors on the active region of the substrate, each of the first to third transistors including a dielectric layer on the substrate, a metal layer on the dielectric layer, a barrier layer between the dielectric layer and the metal layer, and a work function layer between the dielectric layer and the barrier layer, wherein the barrier layer of the third transistor is in contact with the dielectric layer of the third transistor, and wherein a threshold voltage of the second transistor is greater than a threshold voltage of the first transistor and less than a threshold voltage of the third transistor.

What is claimed is: 
     
       1. A semiconductor device, comprising:
 a substrate having an active region; and 
 first to third transistors on the active region of the substrate, each of the first to third transistors including:
 a dielectric layer on the substrate, 
 a metal layer on the dielectric layer, and 
 a barrier layer between the dielectric layer and the metal layer, 
 
 wherein each of the first and second transistors further includes a work function layer between the dielectric layer and the barrier layer, 
 wherein the barrier layer of the third transistor is in contact with the dielectric layer of the third transistor, and 
 wherein a threshold voltage of the second transistor is greater than a threshold voltage of the first transistor and less than a threshold voltage of the third transistor. 
 
     
     
       2. The device as claimed in  claim 1 , wherein a thickness of the work function layer of the second transistor is greater than a thickness of the work function layer of the first transistor. 
     
     
       3. The device as claimed in  claim 1 , wherein the work function layer of each of the first and second transistors includes a lower work function layer and an upper work function layer on the lower work function layer. 
     
     
       4. The device as claimed in  claim 3 , wherein:
 a thickness of the lower work function layer of the second transistor is greater than a thickness of the lower work function layer of the first transistor, and 
 a thickness of the upper work function layer of the second transistor is the same as a thickness of the upper work function layer of the first transistor. 
 
     
     
       5. The device as claimed in  claim 1 , wherein a thickness of the barrier layer of the third transistor is substantially the same as a sum of a thickness of the work function layer of the first transistor and a thickness of the barrier layer of the first transistor. 
     
     
       6. The device as claimed in  claim 1 , wherein a top surface of the barrier layer of the third transistor is at a level the same as or lower than that of a top surface of the barrier layer of the second transistor. 
     
     
       7. The device as claimed in  claim 1 , wherein:
 the barrier layer of each of the first and second transistors includes a lower barrier layer and an upper barrier layer on the lower barrier layer, and 
 the upper barrier layer of each of the first and second transistors includes substantially the same material as that of the barrier layer of the third transistor. 
 
     
     
       8. The device as claimed in  claim 1 , wherein:
 each of the first to third transistors is provided in plural, and 
 the dielectric layer of one of the plurality of first transistors, of one of the plurality of second transistors, and of one of the plurality of third transistors further comprises a work function control element. 
 
     
     
       9. The device as claimed in  claim 8 , wherein a threshold voltage of the one transistor of the plurality of first transistors that includes the work function control element is less than a threshold voltage of a first transistor of the plurality of first transistors including no work function control element.